1. Field of the Invention
The invention relates generally to a hydromechanical drive system consisting of a swash-plate type hydrostatic axial piston engine and a mechanical transmission such as a geared transmission. The axial piston engine has a cylindrical drum provided with working cylinders and a control surface onto which hydraulic-medium channels open so that the working cylinders are periodically connected with the hydraulic-medium channels during rotation of the cylindrical drum.
2. Description of Related Prior art
A hydromechanical drive system for driving a crawler track or for use as the gear drive for a work vehicle is disclosed in U.S. Pat. No. 4,583,425 which is incorporated herein by reference. In this prior art drive system, the axial piston engine is partially integrated into the transmission. The cylindrical drum and the swash plate of the axial piston engine and the surrounding housing are located in a hollow space of the planet carrier of the last stage of the planetary transmission. This arrangement reduces the axial structural length of the drive system as compared to other hydromechanical drive systems. However, the radial dimensions of this system are greater than the radial dimensions of a single axial piston engine which is disadvantageous. Furthermore, in connection with the axial length of the drive system, the control base receptacle is provided with hydraulic-medium channels for the delivery and return of a hydraulic medium.